exif-data.c

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/* exif-data.c
 *
 * Copyright (c) 2001 Lutz Mueller <lutz@users.sourceforge.net>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the
 * Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor,
 * Boston, MA  02110-1301  USA.
 */

#include <config.h>

#include <libexif/exif-mnote-data.h>
#include <libexif/exif-data.h>
#include <libexif/exif-ifd.h>
#include <libexif/exif-mnote-data-priv.h>
#include <libexif/exif-utils.h>
#include <libexif/exif-loader.h>
#include <libexif/exif-log.h>
#include <libexif/i18n.h>
#include <libexif/exif-system.h>

#include <libexif/canon/exif-mnote-data-canon.h>
#include <libexif/fuji/exif-mnote-data-fuji.h>
#include <libexif/olympus/exif-mnote-data-olympus.h>
#include <libexif/pentax/exif-mnote-data-pentax.h>

#include <stdlib.h>
#include <stdio.h>
#include <string.h>

#undef JPEG_MARKER_SOI
#define JPEG_MARKER_SOI  0xd8
#undef JPEG_MARKER_APP0
#define JPEG_MARKER_APP0 0xe0
#undef JPEG_MARKER_APP1
#define JPEG_MARKER_APP1 0xe1

static const unsigned char ExifHeader[] = {0x45, 0x78, 0x69, 0x66, 0x00, 0x00};

struct _ExifDataPrivate
{
        ExifByteOrder order;

        ExifMnoteData *md;

        ExifLog *log;
        ExifMem *mem;

        unsigned int ref_count;

        /* Temporarily used while loading data */
        unsigned int offset_mnote;

        ExifDataOption options;
        ExifDataType data_type;
};

static void *
exif_data_alloc (ExifData *data, unsigned int i)
{
        void *d;

        if (!data || !i) 
                return NULL;

        d = exif_mem_alloc (data->priv->mem, i);
        if (d) 
                return d;

        EXIF_LOG_NO_MEMORY (data->priv->log, "ExifData", i);
        return NULL;
}

ExifMnoteData *
exif_data_get_mnote_data (ExifData *d)
{
        return (d && d->priv) ? d->priv->md : NULL;
}

ExifData *
exif_data_new (void)
{
        ExifMem *mem = exif_mem_new_default ();
        ExifData *d = exif_data_new_mem (mem);

        exif_mem_unref (mem);

        return d;
}

ExifData *
exif_data_new_mem (ExifMem *mem)
{
        ExifData *data;
        unsigned int i;

        if (!mem) 
                return NULL;

        data = exif_mem_alloc (mem, sizeof (ExifData));
        if (!data) 
                return (NULL);
        data->priv = exif_mem_alloc (mem, sizeof (ExifDataPrivate));
        if (!data->priv) { 
                exif_mem_free (mem, data); 
                return (NULL); 
        }
        data->priv->ref_count = 1;

        data->priv->mem = mem;
        exif_mem_ref (mem);

        for (i = 0; i < EXIF_IFD_COUNT; i++) {
                data->ifd[i] = exif_content_new_mem (data->priv->mem);
                if (!data->ifd[i]) {
                        exif_data_free (data);
                        return (NULL);
                }
                data->ifd[i]->parent = data;
        }

        /* Default options */
#ifndef NO_VERBOSE_TAG_STRINGS
        /*
         * When the tag list is compiled away, setting this option prevents
         * any tags from being loaded
         */
        exif_data_set_option (data, EXIF_DATA_OPTION_IGNORE_UNKNOWN_TAGS);
#endif
        exif_data_set_option (data, EXIF_DATA_OPTION_FOLLOW_SPECIFICATION);

        /* Default data type: none */
        exif_data_set_data_type (data, EXIF_DATA_TYPE_COUNT);

        return (data);
}

ExifData *
exif_data_new_from_data (const unsigned char *data, unsigned int size)
{
        ExifData *edata;

        edata = exif_data_new ();
        exif_data_load_data (edata, data, size);
        return (edata);
}

static int
exif_data_load_data_entry (ExifData *data, ExifEntry *entry,
                           const unsigned char *d,
                           unsigned int size, unsigned int offset)
{
        unsigned int s, doff;

        entry->tag        = exif_get_short (d + offset + 0, data->priv->order);
        entry->format     = exif_get_short (d + offset + 2, data->priv->order);
        entry->components = exif_get_long  (d + offset + 4, data->priv->order);

        /* FIXME: should use exif_tag_get_name_in_ifd here but entry->parent 
         * has not been set yet
         */
        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                  "Loading entry 0x%x ('%s')...", entry->tag,
                  exif_tag_get_name (entry->tag));

        /* {0,1,2,4,8} x { 0x00000000 .. 0xffffffff } 
         *   -> { 0x000000000 .. 0x7fffffff8 } */
        s = exif_format_get_size(entry->format) * entry->components;
        if ((s < entry->components) || (s == 0)){
                return 0;
        }

        /*
         * Size? If bigger than 4 bytes, the actual data is not
         * in the entry but somewhere else (offset).
         */
        if (s > 4)
                doff = exif_get_long (d + offset + 8, data->priv->order);
        else
                doff = offset + 8;

        /* Sanity checks */
        if ((doff + s < doff) || (doff + s < s) || (doff + s > size)) {
                exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                                  "Tag data past end of buffer (%u > %u)", doff+s, size);       
                return 0;
        }

        entry->data = exif_data_alloc (data, s);
        if (entry->data) {
                entry->size = s;
                memcpy (entry->data, d + doff, s);
        } else {
                /* FIXME: What do our callers do if (entry->data == NULL)? */
                EXIF_LOG_NO_MEMORY(data->priv->log, "ExifData", s);
        }

        /* If this is the MakerNote, remember the offset */
        if (entry->tag == EXIF_TAG_MAKER_NOTE) {
                if (!entry->data) {
                        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                                          "MakerNote found with empty data");   
                } else if (entry->size > 6) {
                        exif_log (data->priv->log,
                                               EXIF_LOG_CODE_DEBUG, "ExifData",
                                               "MakerNote found (%02x %02x %02x %02x "
                                               "%02x %02x %02x...).",
                                               entry->data[0], entry->data[1], entry->data[2],
                                               entry->data[3], entry->data[4], entry->data[5],
                                               entry->data[6]);
                }
                data->priv->offset_mnote = doff;
        }
        return 1;
}

static void
exif_data_save_data_entry (ExifData *data, ExifEntry *e,
                           unsigned char **d, unsigned int *ds,
                           unsigned int offset)
{
        unsigned int doff, s;
        unsigned int ts;

        if (!data || !data->priv) 
                return;

        /*
         * Each entry is 12 bytes long. The memory for the entry has
         * already been allocated.
         */
        exif_set_short (*d + 6 + offset + 0,
                        data->priv->order, (ExifShort) e->tag);
        exif_set_short (*d + 6 + offset + 2,
                        data->priv->order, (ExifShort) e->format);

        if (!(data->priv->options & EXIF_DATA_OPTION_DONT_CHANGE_MAKER_NOTE)) {
                /* If this is the maker note tag, update it. */
                if ((e->tag == EXIF_TAG_MAKER_NOTE) && data->priv->md) {
                        /* TODO: this is using the wrong ExifMem to free e->data */
                        exif_mem_free (data->priv->mem, e->data);
                        e->data = NULL;
                        e->size = 0;
                        exif_mnote_data_set_offset (data->priv->md, *ds - 6);
                        exif_mnote_data_save (data->priv->md, &e->data, &e->size);
                        e->components = e->size;
                }
        }

        exif_set_long  (*d + 6 + offset + 4,
                        data->priv->order, e->components);

        /*
         * Size? If bigger than 4 bytes, the actual data is not in
         * the entry but somewhere else.
         */
        s = exif_format_get_size (e->format) * e->components;
        if (s > 4) {
                unsigned char *t;
                doff = *ds - 6;
                ts = *ds + s;

                /*
                 * According to the TIFF specification,
                 * the offset must be an even number. If we need to introduce
                 * a padding byte, we set it to 0.
                 */
                if (s & 1)
                        ts++;
                t = exif_mem_realloc (data->priv->mem, *d, ts);
                if (!t) {
                        EXIF_LOG_NO_MEMORY (data->priv->log, "ExifData", ts);
                        return;
                }
                *d = t;
                *ds = ts;
                exif_set_long (*d + 6 + offset + 8, data->priv->order, doff);
                if (s & 1) 
                        *(*d + *ds - 1) = '\0';

        } else
                doff = offset + 8;

        /* Write the data. Fill unneeded bytes with 0. Do not crash with
         * e->data is NULL */
        if (e->data) {
                memcpy (*d + 6 + doff, e->data, s);
        } else {
                memset (*d + 6 + doff, 0, s);
        }
        if (s < 4) 
                memset (*d + 6 + doff + s, 0, (4 - s));
}

static void
exif_data_load_data_thumbnail (ExifData *data, const unsigned char *d,
                               unsigned int ds, ExifLong o, ExifLong s)
{
        /* Sanity checks */
        if ((o + s < o) || (o + s < s) || (o + s > ds) || (o > ds)) {
                exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                          "Bogus thumbnail offset (%u) or size (%u).",
                          o, s);
                return;
        }

        if (data->data) 
                exif_mem_free (data->priv->mem, data->data);
        if (!(data->data = exif_data_alloc (data, s))) {
                EXIF_LOG_NO_MEMORY (data->priv->log, "ExifData", s);
                data->size = 0;
                return;
        }
        data->size = s;
        memcpy (data->data, d + o, s);
}

#undef CHECK_REC
#define CHECK_REC(i)                                    \
if ((i) == ifd) {                               \
        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, \
                "ExifData", "Recursive entry in IFD "   \
                "'%s' detected. Skipping...",           \
                exif_ifd_get_name (i));                 \
        break;                                          \
}                                                       \
if (data->ifd[(i)]->count) {                            \
        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, \
                "ExifData", "Attempt to load IFD "      \
                "'%s' multiple times detected. "        \
                "Skipping...",                          \
                exif_ifd_get_name (i));                 \
        break;                                          \
}

static void
exif_data_load_data_content (ExifData *data, ExifIfd ifd,
                             const unsigned char *d,
                             unsigned int ds, unsigned int offset, unsigned int recursion_depth)
{
        ExifLong o, thumbnail_offset = 0, thumbnail_length = 0;
        ExifShort n;
        ExifEntry *entry;
        unsigned int i;
        ExifTag tag;

        if (!data || !data->priv) 
                return;

        /* check for valid ExifIfd enum range */
        if ((((int)ifd) < 0) || ( ((int)ifd) >= EXIF_IFD_COUNT))
          return;

        if (recursion_depth > 30) {
                exif_log (data->priv->log, EXIF_LOG_CODE_CORRUPT_DATA, "ExifData",
                          "Deep recursion detected!");
                return;
        }

        /* Read the number of entries */
        if ((offset + 2 < offset) || (offset + 2 < 2) || (offset + 2 > ds)) {
                exif_log (data->priv->log, EXIF_LOG_CODE_CORRUPT_DATA, "ExifData",
                          "Tag data past end of buffer (%u > %u)", offset+2, ds);
                return;
        }
        n = exif_get_short (d + offset, data->priv->order);
        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                  "Loading %hu entries...", n);
        offset += 2;

        /* Check if we have enough data. */
        if (offset + 12 * n > ds) {
                n = (ds - offset) / 12;
                exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                                  "Short data; only loading %hu entries...", n);
        }

        for (i = 0; i < n; i++) {

                tag = exif_get_short (d + offset + 12 * i, data->priv->order);
                switch (tag) {
                case EXIF_TAG_EXIF_IFD_POINTER:
                case EXIF_TAG_GPS_INFO_IFD_POINTER:
                case EXIF_TAG_INTEROPERABILITY_IFD_POINTER:
                case EXIF_TAG_JPEG_INTERCHANGE_FORMAT_LENGTH:
                case EXIF_TAG_JPEG_INTERCHANGE_FORMAT:
                        o = exif_get_long (d + offset + 12 * i + 8,
                                           data->priv->order);
                        /* FIXME: IFD_POINTER tags aren't marked as being in a
                         * specific IFD, so exif_tag_get_name_in_ifd won't work
                         */
                        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                                  "Sub-IFD entry 0x%x ('%s') at %u.", tag,
                                  exif_tag_get_name(tag), o);
                        switch (tag) {
                        case EXIF_TAG_EXIF_IFD_POINTER:
                                CHECK_REC (EXIF_IFD_EXIF);
                                exif_data_load_data_content (data, EXIF_IFD_EXIF, d, ds, o, recursion_depth + 1);
                                break;
                        case EXIF_TAG_GPS_INFO_IFD_POINTER:
                                CHECK_REC (EXIF_IFD_GPS);
                                exif_data_load_data_content (data, EXIF_IFD_GPS, d, ds, o, recursion_depth + 1);
                                break;
                        case EXIF_TAG_INTEROPERABILITY_IFD_POINTER:
                                CHECK_REC (EXIF_IFD_INTEROPERABILITY);
                                exif_data_load_data_content (data, EXIF_IFD_INTEROPERABILITY, d, ds, o, recursion_depth + 1);
                                break;
                        case EXIF_TAG_JPEG_INTERCHANGE_FORMAT:
                                thumbnail_offset = o;
                                if (thumbnail_offset && thumbnail_length)
                                        exif_data_load_data_thumbnail (data, d,
                                                                       ds, thumbnail_offset,
                                                                       thumbnail_length);
                                break;
                        case EXIF_TAG_JPEG_INTERCHANGE_FORMAT_LENGTH:
                                thumbnail_length = o;
                                if (thumbnail_offset && thumbnail_length)
                                        exif_data_load_data_thumbnail (data, d,
                                                                       ds, thumbnail_offset,
                                                                       thumbnail_length);
                                break;
                        default:
                                return;
                        }
                        break;
                default:

                        /*
                         * If we don't know the tag, don't fail. It could be that new 
                         * versions of the standard have defined additional tags. Note that
                         * 0 is a valid tag in the GPS IFD.
                         */
                        if (!exif_tag_get_name_in_ifd (tag, ifd)) {

                                /*
                                 * Special case: Tag and format 0. That's against specification
                                 * (at least up to 2.2). But Photoshop writes it anyways.
                                 */
                                if (!memcmp (d + offset + 12 * i, "\0\0\0\0", 4)) {
                                        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                                                  "Skipping empty entry at position %u in '%s'.", i, 
                                                  exif_ifd_get_name (ifd));
                                        break;
                                }
                                exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                                          "Unknown tag 0x%04x (entry %u in '%s'). Please report this tag "
                                          "to <libexif-devel@lists.sourceforge.net>.", tag, i,
                                          exif_ifd_get_name (ifd));
                                if (data->priv->options & EXIF_DATA_OPTION_IGNORE_UNKNOWN_TAGS)
                                        break;
                        }
                        entry = exif_entry_new_mem (data->priv->mem);
                        if (exif_data_load_data_entry (data, entry, d, ds,
                                                   offset + 12 * i))
                                exif_content_add_entry (data->ifd[ifd], entry);
                        exif_entry_unref (entry);
                        break;
                }
        }
}

static int
cmp_func (const unsigned char *p1, const unsigned char *p2, ExifByteOrder o)
{
        ExifShort tag1 = exif_get_short (p1, o);
        ExifShort tag2 = exif_get_short (p2, o);

        return (tag1 < tag2) ? -1 : (tag1 > tag2) ? 1 : 0;
}

static int
cmp_func_intel (const void *elem1, const void *elem2)
{
        return cmp_func ((const unsigned char *) elem1,
                         (const unsigned char *) elem2, EXIF_BYTE_ORDER_INTEL);
}

static int
cmp_func_motorola (const void *elem1, const void *elem2)
{
        return cmp_func ((const unsigned char *) elem1,
                         (const unsigned char *) elem2, EXIF_BYTE_ORDER_MOTOROLA);
}

static void
exif_data_save_data_content (ExifData *data, ExifContent *ifd,
                             unsigned char **d, unsigned int *ds,
                             unsigned int offset)
{
        unsigned int j, n_ptr = 0, n_thumb = 0;
        ExifIfd i;
        unsigned char *t;
        unsigned int ts;

        if (!data || !data->priv || !ifd || !d || !ds) 
                return;

        for (i = 0; i < EXIF_IFD_COUNT; i++)
                if (ifd == data->ifd[i])
                        break;
        if (i == EXIF_IFD_COUNT)
                return; /* error */

        /*
         * Check if we need some extra entries for pointers or the thumbnail.
         */
        switch (i) {
        case EXIF_IFD_0:

                /*
                 * The pointer to IFD_EXIF is in IFD_0. The pointer to
                 * IFD_INTEROPERABILITY is in IFD_EXIF.
                 */
                if (data->ifd[EXIF_IFD_EXIF]->count ||
                    data->ifd[EXIF_IFD_INTEROPERABILITY]->count)
                        n_ptr++;

                /* The pointer to IFD_GPS is in IFD_0. */
                if (data->ifd[EXIF_IFD_GPS]->count)
                        n_ptr++;

                break;
        case EXIF_IFD_1:
                if (data->size)
                        n_thumb = 2;
                break;
        case EXIF_IFD_EXIF:
                if (data->ifd[EXIF_IFD_INTEROPERABILITY]->count)
                        n_ptr++;
        default:
                break;
        }

        /*
         * Allocate enough memory for all entries
         * and the number of entries.
         */
        ts = *ds + (2 + (ifd->count + n_ptr + n_thumb) * 12 + 4);
        t = exif_mem_realloc (data->priv->mem, *d, ts);
        if (!t) {
                EXIF_LOG_NO_MEMORY (data->priv->log, "ExifData", ts);
                return;
        }
        *d = t;
        *ds = ts;

        /* Save the number of entries */
        exif_set_short (*d + 6 + offset, data->priv->order,
                        (ExifShort) (ifd->count + n_ptr + n_thumb));
        offset += 2;

        /*
         * Save each entry. Make sure that no memcpys from NULL pointers are
         * performed
         */
        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                  "Saving %i entries (IFD '%s', offset: %i)...",
                  ifd->count, exif_ifd_get_name (i), offset);
        for (j = 0; j < ifd->count; j++) {
                if (ifd->entries[j]) {
                        exif_data_save_data_entry (data, ifd->entries[j], d, ds,
                                offset + 12 * j);
                }
        }

        offset += 12 * ifd->count;

        /* Now save special entries. */
        switch (i) {
        case EXIF_IFD_0:

                /*
                 * The pointer to IFD_EXIF is in IFD_0.
                 * However, the pointer to IFD_INTEROPERABILITY is in IFD_EXIF,
                 * therefore, if IFD_INTEROPERABILITY is not empty, we need
                 * IFD_EXIF even if latter is empty.
                 */
                if (data->ifd[EXIF_IFD_EXIF]->count ||
                    data->ifd[EXIF_IFD_INTEROPERABILITY]->count) {
                        exif_set_short (*d + 6 + offset + 0, data->priv->order,
                                        EXIF_TAG_EXIF_IFD_POINTER);
                        exif_set_short (*d + 6 + offset + 2, data->priv->order,
                                        EXIF_FORMAT_LONG);
                        exif_set_long  (*d + 6 + offset + 4, data->priv->order,
                                        1);
                        exif_set_long  (*d + 6 + offset + 8, data->priv->order,
                                        *ds - 6);
                        exif_data_save_data_content (data,
                                                     data->ifd[EXIF_IFD_EXIF], d, ds, *ds - 6);
                        offset += 12;
                }

                /* The pointer to IFD_GPS is in IFD_0, too. */
                if (data->ifd[EXIF_IFD_GPS]->count) {
                        exif_set_short (*d + 6 + offset + 0, data->priv->order,
                                        EXIF_TAG_GPS_INFO_IFD_POINTER);
                        exif_set_short (*d + 6 + offset + 2, data->priv->order,
                                        EXIF_FORMAT_LONG);
                        exif_set_long  (*d + 6 + offset + 4, data->priv->order,
                                        1);
                        exif_set_long  (*d + 6 + offset + 8, data->priv->order,
                                        *ds - 6);
                        exif_data_save_data_content (data,
                                                     data->ifd[EXIF_IFD_GPS], d, ds, *ds - 6);
                        offset += 12;
                }

                break;
        case EXIF_IFD_EXIF:

                /*
                 * The pointer to IFD_INTEROPERABILITY is in IFD_EXIF.
                 * See note above.
                 */
                if (data->ifd[EXIF_IFD_INTEROPERABILITY]->count) {
                        exif_set_short (*d + 6 + offset + 0, data->priv->order,
                                        EXIF_TAG_INTEROPERABILITY_IFD_POINTER);
                        exif_set_short (*d + 6 + offset + 2, data->priv->order,
                                        EXIF_FORMAT_LONG);
                        exif_set_long  (*d + 6 + offset + 4, data->priv->order,
                                        1);
                        exif_set_long  (*d + 6 + offset + 8, data->priv->order,
                                        *ds - 6);
                        exif_data_save_data_content (data,
                                                     data->ifd[EXIF_IFD_INTEROPERABILITY], d, ds,
                                                     *ds - 6);
                        offset += 12;
                }

                break;
        case EXIF_IFD_1:

                /*
                 * Information about the thumbnail (if any) is saved in
                 * IFD_1.
                 */
                if (data->size) {

                        /* EXIF_TAG_JPEG_INTERCHANGE_FORMAT */
                        exif_set_short (*d + 6 + offset + 0, data->priv->order,
                                        EXIF_TAG_JPEG_INTERCHANGE_FORMAT);
                        exif_set_short (*d + 6 + offset + 2, data->priv->order,
                                        EXIF_FORMAT_LONG);
                        exif_set_long  (*d + 6 + offset + 4, data->priv->order,
                                        1);
                        exif_set_long  (*d + 6 + offset + 8, data->priv->order,
                                        *ds - 6);
                        ts = *ds + data->size;
                        t = exif_mem_realloc (data->priv->mem, *d, ts);
                        if (!t) {
                                EXIF_LOG_NO_MEMORY (data->priv->log, "ExifData",
                                                    ts);
                                return;
                        }
                        *d = t;
                        *ds = ts;
                        memcpy (*d + *ds - data->size, data->data, data->size);
                        offset += 12;

                        /* EXIF_TAG_JPEG_INTERCHANGE_FORMAT_LENGTH */
                        exif_set_short (*d + 6 + offset + 0, data->priv->order,
                                        EXIF_TAG_JPEG_INTERCHANGE_FORMAT_LENGTH);
                        exif_set_short (*d + 6 + offset + 2, data->priv->order,
                                        EXIF_FORMAT_LONG);
                        exif_set_long  (*d + 6 + offset + 4, data->priv->order,
                                        1);
                        exif_set_long  (*d + 6 + offset + 8, data->priv->order,
                                        data->size);
                        offset += 12;
                }

                break;
        default:
                break;
        }

        /* Sort the directory according to TIFF specification */
        qsort (*d + 6 + offset - (ifd->count + n_ptr + n_thumb) * 12,
               (ifd->count + n_ptr + n_thumb), 12,
               (data->priv->order == EXIF_BYTE_ORDER_INTEL) ? cmp_func_intel : cmp_func_motorola);

        /* Correctly terminate the directory */
        if (i == EXIF_IFD_0 && (data->ifd[EXIF_IFD_1]->count ||
                                data->size)) {

                /*
                 * We are saving IFD 0. Tell where IFD 1 starts and save
                 * IFD 1.
                 */
                exif_set_long (*d + 6 + offset, data->priv->order, *ds - 6);
                exif_data_save_data_content (data, data->ifd[EXIF_IFD_1], d, ds,
                                             *ds - 6);
        } else
                exif_set_long (*d + 6 + offset, data->priv->order, 0);
}

typedef enum {
        EXIF_DATA_TYPE_MAKER_NOTE_NONE          = 0,
        EXIF_DATA_TYPE_MAKER_NOTE_CANON         = 1,
        EXIF_DATA_TYPE_MAKER_NOTE_OLYMPUS       = 2,
        EXIF_DATA_TYPE_MAKER_NOTE_PENTAX        = 3,
        EXIF_DATA_TYPE_MAKER_NOTE_NIKON         = 4,
        EXIF_DATA_TYPE_MAKER_NOTE_CASIO         = 5,
        EXIF_DATA_TYPE_MAKER_NOTE_FUJI          = 6
} ExifDataTypeMakerNote;

static void
interpret_maker_note(ExifData *data, const unsigned char *d, unsigned int ds)
{
        int mnoteid;
        ExifEntry* e = exif_data_get_entry (data, EXIF_TAG_MAKER_NOTE);
        if (!e)
                return;
        
        if ((mnoteid = exif_mnote_data_olympus_identify (data, e)) != 0) {
                exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG,
                        "ExifData", "Olympus MakerNote variant type %d", mnoteid);
                data->priv->md = exif_mnote_data_olympus_new (data->priv->mem);

        } else if ((mnoteid = exif_mnote_data_canon_identify (data, e)) != 0) {
                exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG,
                        "ExifData", "Canon MakerNote variant type %d", mnoteid);
                data->priv->md = exif_mnote_data_canon_new (data->priv->mem, data->priv->options);

        } else if ((mnoteid = exif_mnote_data_fuji_identify (data, e)) != 0) {
                exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG,
                        "ExifData", "Fuji MakerNote variant type %d", mnoteid);
                data->priv->md = exif_mnote_data_fuji_new (data->priv->mem);

        /* NOTE: Must do Pentax detection last because some of the
         * heuristics are pretty general. */
        } else if ((mnoteid = exif_mnote_data_pentax_identify (data, e)) != 0) {
                exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG,
                        "ExifData", "Pentax MakerNote variant type %d", mnoteid);
                data->priv->md = exif_mnote_data_pentax_new (data->priv->mem);
        }

        /* 
         * If we are able to interpret the maker note, do so.
         */
        if (data->priv->md) {
                exif_mnote_data_log (data->priv->md, data->priv->log);
                exif_mnote_data_set_byte_order (data->priv->md,
                                                data->priv->order);
                exif_mnote_data_set_offset (data->priv->md,
                                            data->priv->offset_mnote);
                exif_mnote_data_load (data->priv->md, d, ds);
        }
}

#define LOG_TOO_SMALL \
exif_log (data->priv->log, EXIF_LOG_CODE_CORRUPT_DATA, "ExifData", \
                _("Size of data too small to allow for EXIF data."));

void
exif_data_load_data (ExifData *data, const unsigned char *d_orig,
                     unsigned int ds)
{
        unsigned int l;
        ExifLong offset;
        ExifShort n;
        const unsigned char *d = d_orig;
        unsigned int len, fullds;

        if (!data || !data->priv || !d || !ds)
                return;

        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                  "Parsing %i byte(s) EXIF data...\n", ds);

        /*
         * It can be that the data starts with the EXIF header. If it does
         * not, search the EXIF marker.
         */
        if (ds < 6) {
                LOG_TOO_SMALL;
                return;
        }
        if (!memcmp (d, ExifHeader, 6)) {
                exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                          "Found EXIF header.");
        } else {
                while (ds >= 3) {
                        while (ds && (d[0] == 0xff)) {
                                d++;
                                ds--;
                        }

                        /* JPEG_MARKER_SOI */
                        if (ds && d[0] == JPEG_MARKER_SOI) {
                                d++;
                                ds--;
                                continue;
                        }

                        /* JPEG_MARKER_APP0 */
                        if (ds >= 3 && d[0] == JPEG_MARKER_APP0) {
                                d++;
                                ds--;
                                l = (d[0] << 8) | d[1];
                                if (l > ds)
                                        return;
                                d += l;
                                ds -= l;
                                continue;
                        }

                        /* JPEG_MARKER_APP1 */
                        if (ds && d[0] == JPEG_MARKER_APP1)
                                break;

                        /* Unknown marker or data. Give up. */
                        exif_log (data->priv->log, EXIF_LOG_CODE_CORRUPT_DATA,
                                  "ExifData", _("EXIF marker not found."));
                        return;
                }
                if (ds < 3) {
                        LOG_TOO_SMALL;
                        return;
                }
                d++;
                ds--;
                len = (d[0] << 8) | d[1];
                exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                          "We have to deal with %i byte(s) of EXIF data.",
                          len);
                d += 2;
                ds -= 2;
        }

        /*
         * Verify the exif header
         * (offset 2, length 6).
         */
        if (ds < 6) {
                LOG_TOO_SMALL;
                return;
        }
        if (memcmp (d, ExifHeader, 6)) {
                exif_log (data->priv->log, EXIF_LOG_CODE_CORRUPT_DATA,
                          "ExifData", _("EXIF header not found."));
                return;
        }

        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                  "Found EXIF header.");

        /* Sanity check the data length */
        if (ds < 14)
                return;

        /* The JPEG APP1 section can be no longer than 64 KiB (including a
           16-bit length), so cap the data length to protect against overflow
           in future offset calculations */
        fullds = ds;
        if (ds > 0xfffe)
                ds = 0xfffe;

        /* Byte order (offset 6, length 2) */
        if (!memcmp (d + 6, "II", 2))
                data->priv->order = EXIF_BYTE_ORDER_INTEL;
        else if (!memcmp (d + 6, "MM", 2))
                data->priv->order = EXIF_BYTE_ORDER_MOTOROLA;
        else {
                exif_log (data->priv->log, EXIF_LOG_CODE_CORRUPT_DATA,
                          "ExifData", _("Unknown encoding."));
                return;
        }

        /* Fixed value */
        if (exif_get_short (d + 8, data->priv->order) != 0x002a)
                return;

        /* IFD 0 offset */
        offset = exif_get_long (d + 10, data->priv->order);
        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData", 
                  "IFD 0 at %i.", (int) offset);

        /* Sanity check the offset, being careful about overflow */
        if (offset > ds || offset + 6 + 2 > ds)
                return;

        /* Parse the actual exif data (usually offset 14 from start) */
        exif_data_load_data_content (data, EXIF_IFD_0, d + 6, ds - 6, offset, 0);

        /* IFD 1 offset */
        n = exif_get_short (d + 6 + offset, data->priv->order);
        if (offset + 6 + 2 + 12 * n + 4 > ds)
                return;

        offset = exif_get_long (d + 6 + offset + 2 + 12 * n, data->priv->order);
        if (offset) {
                exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                          "IFD 1 at %i.", (int) offset);

                /* Sanity check. */
                if (offset > ds || offset + 6 > ds) {
                        exif_log (data->priv->log, EXIF_LOG_CODE_CORRUPT_DATA,
                                  "ExifData", "Bogus offset of IFD1.");
                } else {
                   exif_data_load_data_content (data, EXIF_IFD_1, d + 6, ds - 6, offset, 0);
                }
        }

        /*
         * If we got an EXIF_TAG_MAKER_NOTE, try to interpret it. Some
         * cameras use pointers in the maker note tag that point to the
         * space between IFDs. Here is the only place where we have access
         * to that data.
         */
        interpret_maker_note(data, d, fullds);

        /* Fixup tags if requested */
        if (data->priv->options & EXIF_DATA_OPTION_FOLLOW_SPECIFICATION)
                exif_data_fix (data);
}

void
exif_data_save_data (ExifData *data, unsigned char **d, unsigned int *ds)
{
        if (ds)
                *ds = 0;        /* This means something went wrong */

        if (!data || !d || !ds)
                return;

        /* Header */
        *ds = 14;
        *d = exif_data_alloc (data, *ds);
        if (!*d)  {
                *ds = 0;
                return;
        }
        memcpy (*d, ExifHeader, 6);

        /* Order (offset 6) */
        if (data->priv->order == EXIF_BYTE_ORDER_INTEL) {
                memcpy (*d + 6, "II", 2);
        } else {
                memcpy (*d + 6, "MM", 2);
        }

        /* Fixed value (2 bytes, offset 8) */
        exif_set_short (*d + 8, data->priv->order, 0x002a);

        /*
         * IFD 0 offset (4 bytes, offset 10).
         * We will start 8 bytes after the
         * EXIF header (2 bytes for order, another 2 for the test, and
         * 4 bytes for the IFD 0 offset make 8 bytes together).
         */
        exif_set_long (*d + 10, data->priv->order, 8);

        /* Now save IFD 0. IFD 1 will be saved automatically. */
        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                  "Saving IFDs...");
        exif_data_save_data_content (data, data->ifd[EXIF_IFD_0], d, ds,
                                     *ds - 6);
        exif_log (data->priv->log, EXIF_LOG_CODE_DEBUG, "ExifData",
                  "Saved %i byte(s) EXIF data.", *ds);
}

ExifData *
exif_data_new_from_file (const char *path)
{
        ExifData *edata;
        ExifLoader *loader;

        loader = exif_loader_new ();
        exif_loader_write_file (loader, path);
        edata = exif_loader_get_data (loader);
        exif_loader_unref (loader);

        return (edata);
}

void
exif_data_ref (ExifData *data)
{
        if (!data)
                return;

        data->priv->ref_count++;
}

void
exif_data_unref (ExifData *data)
{
        if (!data) 
                return;

        data->priv->ref_count--;
        if (!data->priv->ref_count) 
                exif_data_free (data);
}

void
exif_data_free (ExifData *data)
{
        unsigned int i;
        ExifMem *mem = (data && data->priv) ? data->priv->mem : NULL;

        if (!data) 
                return;

        for (i = 0; i < EXIF_IFD_COUNT; i++) {
                if (data->ifd[i]) {
                        exif_content_unref (data->ifd[i]);
                        data->ifd[i] = NULL;
                }
        }

        if (data->data) {
                exif_mem_free (mem, data->data);
                data->data = NULL;
        }

        if (data->priv) {
                if (data->priv->log) {
                        exif_log_unref (data->priv->log);
                        data->priv->log = NULL;
                }
                if (data->priv->md) {
                        exif_mnote_data_unref (data->priv->md);
                        data->priv->md = NULL;
                }
                exif_mem_free (mem, data->priv);
                exif_mem_free (mem, data);
        }

        exif_mem_unref (mem);
}

void
exif_data_dump (ExifData *data)
{
        unsigned int i;

        if (!data)
                return;

        for (i = 0; i < EXIF_IFD_COUNT; i++) {
                if (data->ifd[i] && data->ifd[i]->count) {
                        printf ("Dumping IFD '%s'...\n",
                                exif_ifd_get_name (i));
                        exif_content_dump (data->ifd[i], 0);
                }
        }

        if (data->data) {
                printf ("%i byte(s) thumbnail data available.", data->size);
                if (data->size >= 4) {
                        printf ("0x%02x 0x%02x ... 0x%02x 0x%02x\n",
                                data->data[0], data->data[1],
                                data->data[data->size - 2],
                                data->data[data->size - 1]);
                }
        }
}

ExifByteOrder
exif_data_get_byte_order (ExifData *data)
{
        if (!data)
                return (0);

        return (data->priv->order);
}

void
exif_data_foreach_content (ExifData *data, ExifDataForeachContentFunc func,
                           void *user_data)
{
        unsigned int i;

        if (!data || !func)
                return;

        for (i = 0; i < EXIF_IFD_COUNT; i++)
                func (data->ifd[i], user_data);
}

typedef struct _ByteOrderChangeData ByteOrderChangeData;
struct _ByteOrderChangeData {
        ExifByteOrder old, new;
};

static void
entry_set_byte_order (ExifEntry *e, void *data)
{
        ByteOrderChangeData *d = data;

        if (!e)
                return;

        exif_array_set_byte_order (e->format, e->data, e->components, d->old, d->new);
}

static void
content_set_byte_order (ExifContent *content, void *data)
{
        exif_content_foreach_entry (content, entry_set_byte_order, data);
}

void
exif_data_set_byte_order (ExifData *data, ExifByteOrder order)
{
        ByteOrderChangeData d;

        if (!data || (order == data->priv->order))
                return;

        d.old = data->priv->order;
        d.new = order;
        exif_data_foreach_content (data, content_set_byte_order, &d);
        data->priv->order = order;
        if (data->priv->md)
                exif_mnote_data_set_byte_order (data->priv->md, order);
}

void
exif_data_log (ExifData *data, ExifLog *log)
{
        unsigned int i;

        if (!data || !data->priv) 
                return;
        exif_log_unref (data->priv->log);
        data->priv->log = log;
        exif_log_ref (log);

        for (i = 0; i < EXIF_IFD_COUNT; i++)
                exif_content_log (data->ifd[i], log);
}

/* Used internally within libexif */
ExifLog *exif_data_get_log (ExifData *);
ExifLog *
exif_data_get_log (ExifData *data)
{
        if (!data || !data->priv) 
                return NULL;
        return data->priv->log;
}

static const struct {
        ExifDataOption option;
        const char *name;
        const char *description;
} exif_data_option[] = {
        {EXIF_DATA_OPTION_IGNORE_UNKNOWN_TAGS, N_("Ignore unknown tags"),
         N_("Ignore unknown tags when loading EXIF data.")},
        {EXIF_DATA_OPTION_FOLLOW_SPECIFICATION, N_("Follow specification"),
         N_("Add, correct and remove entries to get EXIF data that follows "
            "the specification.")},
        {EXIF_DATA_OPTION_DONT_CHANGE_MAKER_NOTE, N_("Do not change maker note"),
         N_("When loading and resaving Exif data, save the maker note unmodified."
            " Be aware that the maker note can get corrupted.")},
        {0, NULL, NULL}
};

const char *
exif_data_option_get_name (ExifDataOption o)
{
        unsigned int i;

        for (i = 0; exif_data_option[i].name; i++)
                if (exif_data_option[i].option == o) 
                        break;
        return _(exif_data_option[i].name);
}

const char *
exif_data_option_get_description (ExifDataOption o)
{
        unsigned int i;

        for (i = 0; exif_data_option[i].description; i++)
                if (exif_data_option[i].option == o) 
                        break;
        return _(exif_data_option[i].description);
}

void
exif_data_set_option (ExifData *d, ExifDataOption o)
{
        if (!d) 
                return;

        d->priv->options |= o;
}

void
exif_data_unset_option (ExifData *d, ExifDataOption o)
{
        if (!d) 
                return;

        d->priv->options &= ~o;
}

static void
fix_func (ExifContent *c, void *UNUSED(data))
{
        switch (exif_content_get_ifd (c)) {
        case EXIF_IFD_1:
                if (c->parent->data)
                        exif_content_fix (c);
                else if (c->count) {
                        exif_log (c->parent->priv->log, EXIF_LOG_CODE_DEBUG, "exif-data",
                                  "No thumbnail but entries on thumbnail. These entries have been "
                                  "removed.");
                        while (c->count) {
                                unsigned int cnt = c->count;
                                exif_content_remove_entry (c, c->entries[c->count - 1]);
                                if (cnt == c->count) {
                                        /* safety net */
                                        exif_log (c->parent->priv->log, EXIF_LOG_CODE_DEBUG, "exif-data",
                                        "failed to remove last entry from entries.");
                                        c->count--;
                                }
                        }
                }
                break;
        default:
                exif_content_fix (c);
        }
}

void
exif_data_fix (ExifData *d)
{
        exif_data_foreach_content (d, fix_func, NULL);
}

void
exif_data_set_data_type (ExifData *d, ExifDataType dt)
{
        if (!d || !d->priv) 
                return;

        d->priv->data_type = dt;
}

ExifDataType
exif_data_get_data_type (ExifData *d)
{
        return (d && d->priv) ? d->priv->data_type : EXIF_DATA_TYPE_UNKNOWN;
}

---